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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
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    <link
      rel="stylesheet"
      href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css"
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      crossorigin="anonymous"
    />
  </head>
  <body>
    <nav class="nav navbar-inverse navbar-fixed-top">
      <div class="container">
        <div class="navbar-header">
          <!--在移动端的时候导航条折叠起来，三横的样式出现，点击该样式可以显示或隐藏导航条上的内容-->
          <button
            class="navbar-toggle"
            data-toggle="collapse"
            data-target="#menu"
          >
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
          </button>
          <a href="#" class="navbar-brand">logo</a>
        </div>
        <div id="menu" class="collapse navbar-collapse">
          <ul class="nav navbar-nav">
            <li class="active"><a href="#">one</a></li>
            <li><a href="#">two</a></li>
            <!--下拉菜单功能的实现-->
            <li class="dropdown">
              <a href="#" class="dropdown-toggle" data-toggle="dropdown">
                three<span class="caret"></span
              ></a>
              <ul class="dropdown-menu">
                <li><a href="#">first</a></li>
                <li><a href="#">second</a></li>
              </ul>
            </li>
          </ul>
        </div>
      </div>
    </nav>
  </body>
  <script src="./js/jquery-1.11.3.js"></script>
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    src="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/js/bootstrap.min.js"
    integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa"
    crossorigin="anonymous"
  ></script>
</html>
